On 10/09/2015 04:20 AM, Jon Hunter wrote:
On 08/10/15 15:27, Stephen Warren wrote:On 10/08/2015 03:58 AM, Jon Hunter wrote:[snip]That's fine. From my perspective I don't have a strong objection either way, however, I can see that given that the name indicates rx or tx, then the direction in the binding could be seen as redundant. So to confirm you are happy with the client bindings being as follows? tegra_admaif: admaif@0x702d0000 { ... dmas = <&adma 1>, <&adma 1>, <&adma 2>, <&adma 2>, <&adma 3>, <&adma 3>, <&adma 4>, <&adma 4>, <&adma 5>, <&adma 5>, <&adma 6>, <&adma 6>, <&adma 7>, <&adma 7>, <&adma 8>, <&adma 8>, <&adma 9>, <&adma 9>, <&adma 10>, <&adma 10>; dma-names = "rx1", "tx1", "rx2", "tx2", "rx3", "tx3", "rx4", "tx4", "rx5", "tx5", "rx6", "tx6", "rx7", "tx7", "rx8", "tx8", "rx9", "tx9", "rx10", "tx10"; ... };Yes, that looks good for the client binding.One more clarifying question ... should the xlate verify that no other dma channel is using the same hardware request signal? I understand that typically the xlate decodes the binding to get the channel info, but because this is invoked by dmaengine while allocating a channel, I was wondering if we should prevent dmaengine allocating more than one channel to be used with the same hardware request? If so, then passing the direction to the xlate would be necessary (so I can determine in the xlate that no one else is currently using this, which is what I currently do). Alternatively, I could check that no one else is using the request signal at a later when the transfer is being prepared.
I think that handling this at prepare/usage time is probably most appropriate. That is the time when the resource conflict /actually/ occurs.
The only time when two clients would be given the same DMA request signal is if there are multiple different drivers that can DMA into the same FIFO in a time-multiplexed fashion. That seems pretty unlikely off the top of my head, but I don't think we want to actively ban that, in case we come up with a cunning use-case for it.
If you are wondering why I am worried about this, I my mind I think that the driver should be robust enough to check for conflicts in the request signals used by the various channels.
Sure, makes sense. -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
